Monolayer films of U-shaped molecules: suppression of the aggregation-induced second-harmonic generation of squaraine dyes by guest–host interactions

Polymer−Surfactant Layered Heterostructures by Electropolymerization of Phenosafranine in Langmuir−Blodgett Films

“…The film showed circular islands of height ∼3.0-3.5 nm and width ∼200-800 nm as shown in the cross-sectional profile along the line drawn in this figure. The minimum energy configuration for the AA-PS complex obtained from ab initio quantum mechanical optimization ( Figure 7) corresponded to the dimensions 0.997 × 0.768 × 3.026 nm 3 . Hence the height of the islands corresponds to the monolayer thickness.…”

“…3 Conducting polymers are one such material that has attracted considerable interest in recent years. The preparation of high-quality ultrathin films of conducting polymers has great relevance to technological applications such as in sensors 4 and molecular electronics.…”

“…Langmuir-Blodgett (LB) technique is widely used for the fabrication of films of a variety of advanced materials for application in molecular electronics, 1 biosensors, 2 and nonlinear optical (NLO) devices. 3 Conducting polymers are one such material that has attracted considerable interest in recent years. The preparation of high-quality ultrathin films of conducting polymers has great relevance to technological applications such as in sensors 4 and molecular electronics.…”

Exciton Coupling Model for the Emergence of Second Harmonic Generation from Assemblies of Centrosymmetric Molecules

“…In the design of novel organic materials for nonlinear optical applications, it initially appears irrational to consider approaches using molecular building blocks in which second harmonic generation (SHG) activity is strictly forbidden by symmetry. , However, several recent studies have reported the observation of bright SHG from appropriately arranged assemblies of centrosymmetric or nominally centrosymmetric molecules. − The rational use of purely centrosymmetric molecules as building blocks for performing frequency doubling and mixing has the potential to open up entirely new synthetic strategies for the design of organic nonlinear optical (NLO) materials. Rational design hinges first on elucidation of the dominant mechanisms driving the nonlinear optical response.…”

“…In one example using squaraines, SHG activity was observed from Langmuir–Blodgett films prepared using centrosymmetric chromophores. − The presence of SHG activity was attributed to symmetry breaking from interchromophore coupling . An intermolecular charge transfer mechanism was proposed in the case of the squaraines, in which two monomers form a T-shaped dimer.…”